PROJECT SUMMARY Proteins are the central functional instruments that enable life, and the development of strategies for protein mimicry is a grand challenge for chemists. Artificial backbones with defined folding propensities, termed ?foldamers?, can offer biostable analogues of natural entities; however, challenges related to design create barriers to mimicking complex tertiary folds. Overcoming this barrier promises to open a new frontier and advance foldamers toward the functional versatility of proteins. With support from the initial award, a general method for creating foldamer tertiary structure was developed based on the systematic alteration of backbone covalent structure in natural sequences. An important gap remains in establishing the ability of these mimetics to reproduce and modulate functional properties of prototype proteins on which they are based. A long-term goal of the PI?s research program is to develop principles for the design of artificial backbones capable of reproducing the full panoply of protein folds and functions in nature and to apply these principles to control properties such as folded structure, folded stability, physiological stability, and dynamics. The overall objective of this renewal application is to demonstrate the scope of functions possible in heterogeneous-backbone foldamer tertiary structure mimetics. The central hypothesis guiding this work is that design principles developed in the initial award period can be applied to produce functional analogues of diverse prototype proteins and also used to tune functional characteristics of the native backbone. The rationale for pursuing the proposed research is that pushing beyond structural mimicry to functional mimicry in protein-inspired artificial scaffolds will hone design principles, create valuable bioactive agents, and shed new light on natural systems. In order to test the above central hypothesis, two specific aims will be pursued: (1) develop mimics of zinc finger proteins with native-like molecular recognition characteristics; (2) create mimics of disulfide-rich domains from insect and reptile venoms. In terms of expected outcomes, the proposed work will (1) expand the scope of foldamer tertiary structure mimicry (complex chain topologies, large multidomain proteins); (2) broaden the functional repertoire of these scaffolds (selective recognition of DNA, proteins, and biological membranes); (3) yield new insights into the dynamics of sequence-specific DNA binding by zinc finger proteins; and (4) provide a starting point toward bioactive agents with potential applications in the management of chronic pain and treatment of microbial infections. Collectively, realization of the goals of the project will lead to a vertical advance in the size, structural complexity, and functional diversity possible in synthetic protein mimetics.